Nearly six years after the financial crisis began reducing birth rates around the world, people still aren't having many babies. Fewer newborns mean fewer workers in the future producing things and spending.

A trend of smaller families had begun in the 1960s and is already hurting economies. The pool of potential workers -- people ages 20-64 -- had grown rapidly for decades. But now baby boomers are retiring, and there are barely enough new workers to replace them, let alone expand their numbers.

Here are some key facts about the demographic drag on growth:

WHAT'S CHANGED

In the European Union, births fell in 21 of 28 member countries in 2012 vs. 2008 when the crisis began, according to Eurostat, the EU statistics agency. In the four years preceding the crisis, births had fallen in just four of the 28 countries.

In the United States, births fell 7 percent in the same four-year period after decades of increases. In Japan, births fell 5 percent to their lowest level since the 19th century.

Meanwhile, growth in the working-age population has halted in developed countries, on average. In Japan, Germany and Italy, the labor pool is shrinking. Even in France and the United Kingdom, with relatively healthy birth rates, growth in the labor pool has slowed dramatically.

WHY IT MATTERS

Without a continued surge in new workers, many economists argue that developed economies are unlikely to return to "normal" economic growth of 3 percent a year, the average over four decades.

The U.S. economy is projected to grow an average 2.3 percent a year in the eight years beginning in 2017, according to the Congressional Budget Office.

Other estimates are lower. Robert Arnott, chairman of Research Affiliates, thinks the U.S. and other rich countries are likely to grow no more than 1.5 percent a year, on average, over the next several decades.

HIT TO FAMILY INCOME

Slower economic growth will limit wage gains and make it hard for middle-class families to raise their living standards. One measure of living standards is already signaling trouble: Gross domestic product per capita -- the value of goods and services a country produces per person -- fell 1 percent in the five biggest developed countries from 2008 through 2012, according to the World Bank.

HIT TO WEALTH

All else being equal, companies won't make as much in profits in a slower-growing economy. That will weigh down stock prices. And the share of people in the population at the age when they tend to invest in stocks and homes is set to fall, too. That implies stagnant or lower values. Homes are the biggest source of wealth for most middle-class families.